
let _Vue = null;
export default class VueRouter {
  static install(Vue) {
    //1.判断当前插件是否已经被安装
    if (VueRouter.install.installed) return;
    VueRouter.install.installed = true;
    //2.把vue构造函数记录到全局变量
    _Vue = Vue;
    //3.把创建vue实例时候传入的router对象注入到vue实例上
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router;
          this.$options.router.init();
        }
      }
    })
  }

  constructor(options) {
    this.$options = options;
    this.routeMap = {};
    this.data = _Vue.observable({
      current: '/'
    });
  }

  init() {
    this.createRouteMap();
    this.initComponents(_Vue);
    this.initEvent();
  }

  createRouteMap() {
    // 遍历所有的路由规则，把路由规则解析成键值对的形式存在routeMap中
    this.$options.routes.forEach(route => {
      this.routeMap[route.path] = route.component
    })
  }

  // 使用render
  initComponents(Vue) {
    Vue.component('router-link', {
      props: {
        to: String
      },
      render(h) {
        return h(
          'a',
          {
            attrs: {
              href: this.to,
              class: this.$router.data.current === this.to ? 'router-link-exact-active' : ''
            },
            on: {
              click: this.clickHandler
            }
          },
          [this.$slots.default]
        );
      },
      methods: {
        clickHandler(e) {
          history.pushState({}, '', this.to);
          this.$router.data.current = this.to;
          e.preventDefault();
        }
      }
    });
    const self = this;
    Vue.component('router-view', {
      render(h) {
        const component = self.routeMap[self.data.current];
        return h(component);
      }
    });
  }

  initEvent() {
    const eventStr = this.$options.mode === 'history' ? 'popstate' : 'hashchange';
    const keyStr = this.$options.mode === 'history' ? 'pathname' : 'hash';
    console.log(eventStr, keyStr)
    window.addEventListener(eventStr, () => {
      this.data.current = window.location[keyStr];
    })
  }
}